Question: Solve for $q$ : $6 = q + 13$
Subtract $13$ from both sides: $ \begin{eqnarray} \\ \hphantom{6 {- 13}} &\hphantom{=}& \hphantom{q} \\ 6 &=& q + 13 \\ \\ {-13} && {-13} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 6 {- 13} &=& q \\ \end{eqnarray} $ Simplify. $ q = -7$